The Angolan government has freed a 41-year-old British activist to leave its country, nearly one month after charging her with espionage. 

In February, government security forces arrested and jailed Dr. Sara Wykes while she was in the country to meet with government and nonprofit officials to address concerns about corruption in Angola.

As a condition of her release, Wykes has  promised the government she will return to the country if Angolan officials decide to try her. But its unclear whether that will happen, according to Global Witness, the human rights group which employs Wykes. 

After jailing her for several days, Angolan authorities charged Wykes with espionage and released her on bail -- but forbade her from leaving Angola. At no time, she says, was evidence presented against her.

A recent International Monetary Fund report shows the country has taken in almost $18 billion in oil revenue, but at least $4 billion of it has gone missing. Despite the large profits for the government, more than 70 percent of the country's population lives in poverty.

Global Witness, Wykes' employer,  has criticized the Angolan government for taking billions of dollars from oil companies while most of its residents live in poverty.

The group has been lobbying the international community and the U.S. Congress to call for Angola to be more transparent with its oil revenue. 

Fifteen members of Congress, including Senators Barack Obama, D-Ill., Patrick Leahy, D.-Vt., Richard Lugar, R.-Ind. and Rep. Barney Frank, D-Mass. signed letters strongly rebuking the Angolan government's actions. Dr. Wykes also had strong support from the British government, who had been pressuring Angolan authorities for her release.

This post has been revised and updated.